1. Field of the Invention
The present invention relates to a semiconductor laser device having a semiconductor laser and a monitor photodetector device for detecting light emitted from the semiconductor laser.
2. Description of the Related Art
A semiconductor laser employs light emitted from one end (front-side end surface) of its cavity as an original output light. In this case, in order to achieve a lower threshold current, i.e., a lower consumed power and higher reliability, reflectivity Rr at the other end (rear-side end surface) of the optical cavity is generally set as high as possible.
However, a general semiconductor laser device employs a so-called rear-monitoring type arrangement in which light emitted from a rear-side end surface of an optical cavity of a semiconductor laser is detected by a photodetector device formed of a photodiode to obtain a monitor signal and an output from the semiconductor laser is controlled based on the monitor signal. In this case, when a sufficient monitor output is desired, since an attempt of increasing the reflectivity Rr at the rear-side end surface of the optical cavity as described above is restricted, the reflectivity Rr at the rear-side end surface of the semiconductor laser of this kind is usually set to about 80% or smaller.